SYNTHETIC CHEMISTRY, 



39 



horizontal axis ; the second is for tilting it at an angle with the hori- 

 zon ; the third is for turning it about a vertical axis ; and the fourth 

 for raising and lowering it through a range of several inches. 



When a prism like that shown in Fig. 9 is interposed in the path 

 of a narrow beam of sunlight, admitted into a dark room, its alteration 



Pio. 11. 



Equilateral Prism. 



Prism mounted on Stand. 



of the direction of the ray is easily seen, and it will be found that the 

 course of the light is altered, by refraction, some 40° or 50° from its 

 original course. 



The properties of light, to w^hich we have here briefly referred, are 

 interesting in themselves, and important to be known ; but they have 

 additional interest as preparing for an understanding of spectrum 

 analysis, which will be taken up and popularly explained in future 

 numbers of the Monthly. 



SYNTHETIC CHEMISTEY 



By Prof. JOHN W. LANGLEY, ^ 



OF THE WESTERN UNIVERSITT, PENNSYLVANIA. 



CHEMISTRY has been called the analytical science, and undoubt- 

 edly with justice in the past, since the most exact processes with 

 w^hich it deals are still those which go technically by the name of 

 analysis ; but, of recent years, the arts have been enriched by many 

 perfumes, colors, and drugs, which are the results of careful and 



